A machine of this type normally includes an electrically driven motor and a hydraulic unit with an impeller connected to the motor via a rotary driving shaft. In order to prevent the medium within the hydraulic unit from flowing along the shaft and penetrate the electric motor and cause damage, one or several seals are arranged between the motor and the hydraulic unit. A common type of seal is the so-called mechanical face seal, which comprises one seal ring rotating with the shaft and one stationary seal ring mounted in the surrounding housing. The two rings are pressed together by spring force thus preventing medium from penetrating between them.
If the medium within the hydraulic unit contains pollutants, a special problem occurs. As the pressure within the hydraulic unit is higher, pollutants may penetrate between the seal surfaces and cause damage, meaning that the seal result is worsened or fails totally.
In order to solve this problem it is common to arrange two mechanical seals parted by a room filled with a barrier liquid such as oil, which lubricates and cools the surfaces. By this the seal adjacent the electric motor will always operate with a clean medium and thus the risks for damages will decrease drastically. If the seal adjacent the hydraulic unit should be damaged, medium from said unit may enter the barrier liquid room, but by controlling said liquid at regular intervals, the seal could be repaired or replaced before any serious damage has accured. An example on such a design is shown in the Swedish patent No 381 318.
The rotary driving shaft is supported by two bearings, here called the upper and the lower bearing respectively, the latter adjacent the hydraulic unit and located close to the previously mentioned mechanical seal. The bearing, normally a ball bearing, must be lubricated in such a way that metallic contacts between the balls, the treads and the holders are prevented. In addition these surfaces must be prevented from being corroded. If barrier liquid should enter through the seal adjacent the lower bearing, there is a risk that the leakage may brake the lubricating film and generate a bearing brake down.
In order to diminish the above mentioned risk, it has been suggested to arrange a tank for collecting such leakage and store it in such a way that it is prevented from penetrating the bearing and cause damage to the lubricating medium. The storage tank must be big enough to be able to contain all leakage and also be designed in such a way, that the latter is kept parted from the bearing, independent of the operation position of the machine. A machine such as a pump may take lying (horizontal) as well as upright (vertical) operating positions.
In a known design a ring formed chamber is arranged around the barrier liquid housing for collecting leakage. The advantage is that the chamber easily can be dimensioned big enough and that the leakage is kept away from the bearing. A disadvantage is however, that it is large, expensive and requires extended feeding pipes for the barrier liquid.
The purpose of the invention is thus to obtain a storing tank for leakage which tank should require a limited space and be able to store leakage away from the bearing. In addition it should be so designed that it does not constitute an obstacle for the flow within the seal housing, but should add to that flow. This is obtained by help of the device stated in the claims.